1. Field of the Invention
The present invention relates to a radio communication apparatus. More particularly, the present invention relates to an intermittent reception control in a radio communication apparatus.
2. Description of the Related Art
In a radio communication apparatus, an intermittent reception is carried out while a power supply to a radio section requiring a large quantity of electric power is controlled to be turned on and off, in order to make a life of a battery longer.
FIGS. 3A to 3C show an example of a format of a transmission signal received by a radio communication apparatus such as a radio selective call receiver. As shown in FIG. 3A, 15 cycles from 0 to 14 correspond to one hour. The 15 cycles of this one hour unit are continuously sent out for 24 hours. As shown in FIG. 3B, each cycle is composed of 120 transmission frames from 0 to 119. As shown in FIG. 3C, one transmission frame is transmitted in, for example, two seconds. The transmission frame is a basic unit of the reception. The radio communication apparatus can receive all the transmission frames.
One transmission frame is composed of a preamble 1 field of 32 bits, a sync signal 1 field of 32 bits, a preamble 2 field of 16 bits, a sync signal 2 field of 32 bits, a frame information (FI) field of 32 bits and a data field.
A preamble (PR) signal in which xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d are alternately located for 32 bits is stored in the preamble 1 field and used to correct bit synchronization. A sync signal pattern 1 as a particular pattern of 32 bits is stored in the sync signal 1 field and is used to establish word synchronization. A preamble pattern of 16 bits is again stored in the next preamble 2 field. A sync signal pattern 2 is stored in the sync signal 2 field. A data of number of a transmission frame that is being currently transmitted and a cycle number of the transmission frame are stored in the frame information (FI) field. In succession, a message corresponding to at least one identifier (ID) is stored in the data field.
There is a case that all the frames are not transmitted even in a synchronously transmitting system using transmission frames as shown in FIGS. 3A to 3C. Also, there is a case that a part of the transmission frames is used for a transmission using another transmission protocol. In such a case, the transmission is sometimes stopped at a unit of several transmission frames because of the mixture with the other protocol, namely, a transmission stop is carried out.
FIG. 1 shows an example of a manner of the transmission stop in such a synchronization system. Referring to FIG. 1, a period of the transmission stop is not constant, and the number of transmission frames continuously transmitted after the transmission stop is not always constant. The transmission stop is again performed immediately after messages accumulated in the period of the transmission stop are fully transmitted after the start of the transmission. A signal having a different signal format is transmitted during the transmission stop.
In this synchronously transmitting system, the radio communication apparatus determines that the transmission frame is the transmission stop frame, depending upon the reception result. Thus the intermittent reception operation must be carried out on the assumption that there is the transmission of the synchronous transmission frames even during the transmission stop.
A radio communication apparatus for a transmission signal having the synchronous transmission signal format shown in FIGS. 3A to 3C is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 8-149542). In this cited reference, the intermittent reception control is carried out in accordance with a process flow shown in FIG. 2.
Referring to FIG. 2, in a non-synchronous state after a power supply is turned on (Step ST801), a receiving section is turned on (Step ST802). Then, an operation of detecting the sync signal 1 or 2 of the transmission frame is carried out (Step ST803). If any one of the sync signals 1 and 2 is detected, a transmission frame number of the transmission frame is acquired from the frame information (FI) field (Step ST804). The transmission frame synchronization with the transmission signal is established in response to the acquisition of the transmission frame number (Step ST806). After the synchronous establishment, electrical power is supplied to a receiving section at the timing when a transmission start of the transmission frame is predicted (Step ST807), such that the receiving section is set to an ON state (Step ST808). Then, the detection of the sync signal is carried out as mentioned above (Step ST809).
When the sync signal is detected, data is received from the subsequent data field (Step ST810). When the radio communication apparatus determines that the reception of the effective data within this transmission frame is ended, the supply of the electrical power to the receiving section is turned off without waiting for the end of the transmission frame (Step ST811).
If the sync signal is not detected, the supply of the electrical power to the receiving section is stopped at the timing when the transmission end of the sync signal is predicted, and the receiving section is turned off. Then, the radio communication apparatus waits for a next transmission frame (Step ST812).
In the state that the synchronization with the transmission frame is established, the processes from the step ST807 to the step ST812 are repeated for each transmission frame. Thus, the intermittent reception is carried out. The established state of the synchronization with the transmission frame is cancelled when the transmission frame is not received for a predetermined continuous number of times. As a result, the radio communication apparatus is returned back to the non-synchronous state.
In the method shown in FIG. 2 of carrying out the intermittent reception in the established state of the synchronization with the transmission frame, there is no problem if the transmission frames are always transmitted. However, in a case where the transmission stop periods are present, the radio communication apparatus can not discriminate a case where there is the transmission stop between the transmission frames without and a case where there is not transmission stop between the transmission frames, until actually receiving a radio signal. Thus, the receiving section must carry out the detecting operation up to 112 bits (a total bit number of a preamble (PR) field+a sync signal 1 field+a preamble (PR) field+a sync signal 2 field) in the ON state. Therefore, it is said that the conventional radio communication apparatus is not effective from the viewpoint of making the ON time of the receiving section as short as possible.
In addition to the above-mentioned conventional technique, a non-synchronous type of a radio selection call method is disclosed in Japanese Laid Open Patent Application (JP-A-Showa 63-227134). This reference describes a technique of calling a plurality of called parties with a single dial. However, it does not describe the operation of detecting the preamble pattern at all.
Japanese Laid Open Patent Application (JP-A-Heisei 2-153633) discloses a non-synchronous type of a radio selection call receiver that can detect a preamble in a short time. In this reference, a preamble detecting circuit is kept in an ON state for a certain time in a shorter period than a time corresponding to a length of a preamble field. In this reference, the preamble detecting circuit is not kept in the ON state in synchronization with the preamble field. In addition, the preamble detecting circuit is not kept in the ON state in an entire time of the preamble field. The operation of receiving the data is not carried out if the preamble is not detected in this ON time.
Japanese Laid Open Patent Application (JP-A-Heisei 4-304041) discloses a non-synchronous type of a selection call receiver. According to this reference, a one second timer is used to detect a preamble pattern. Thus, the timer must be excessively added to the receiver, which makes the configuration complex. Even when the preamble pattern does not arrive, the operation of detecting the preamble is always carried out. Therefore, since the receiver is always in the ON state, the electrical power is consumed.
Japanese Laid Open Patent Application (JP-A-Heisei 8-98230) discloses a non-synchronous type of a selective call receiver. In this reference, special time information must be added to a transmission frame when a preamble is detected. Thus, this method is not general.
Japanese Laid Open Patent Application (JP-A-Heisei 10-23496) discloses a non-synchronous type of a selection call receiver. In this reference, the consumed electric power is reduced by stopping the receiving operation until a sync signal is received the predetermined number of times after the synchronous establishment. It is described in this reference that the preamble pattern is detected by the intermittent reception before the synchronous establishment. However, it does not actually describe how to detect the preamble pattern.
An object of the present invention is to provide a radio communication apparatus which can control an ON time of a receiving section by detecting the presence or absence of a preamble pattern in a state that synchronization with a transmission frame is established in a synchronously transmitting system, and a method of controlling an intermittent reception thereof.
Another object of the present invention is to provide a radio communication apparatus that can effectively detect a transmission stop period by detecting the presence or absence of a preamble pattern, even in a transmission system using a transmission frame having a transmission stop period, and an intermittent reception method.
In order to achieve an aspect of the present invention, a radio communication apparatus includes a receiving section, a power supply section and a control section. The receiving section receives a radio signal when electric power is supplied, and the radio signal has a preamble field for storing a preamble pattern. The power supply section supplies the electrical power to the receiving section and stopping the supply of the electrical power in response to a supply stop signal. The control section generates the supply stop signal when presence of the preamble pattern can not be detected from the radio signal received by the receiving section, in a state in which a frame synchronization is established.
The control section preferably determines that the preamble pattern is not present, to generate the supply stop signal, when a portion coincident with a predetermined reference pattern is not present within the preamble field. In this case, the control section may includes a clock generating circuit which generates a clock signal, and a counter which counts the clock signal, and generates a preamble end time signal when the counted value reaches a first predetermined value. The control section generates the supply stop signal in response to the preamble end time signal, when the portion coincident with the predetermined reference pattern is not detected within the radio signal received by the receiving section.
Also, the radio signal may have a sync signal field for storing a sync signal and a data field for storing a data, in addition to the preamble field. In this case, the control section may includes a sync signal detecting section which detects the sync signal from the radio signal received by the receiving section to generate a sync signal detection signal without generating the supply stop signal, when the presence of the preamble pattern is detected, and a data receiving section which receives the data from the radio signal received by the receiving section, in response to the sync signal detection signal.
Also, the control section outputs the supply stop signal to the power supply section, when the sync signal is not detected during a predetermined period after the control section detects the preamble pattern.
The counter counts the clock signal to a second predetermined value after counting the first predetermined value, and generates a sync signal end time signal when the count value reaches the second predetermined value. In this case, the control section sends the supply stop signal to the power supply section in response to the sync signal end time signal, when the sync signal is not detected while the counter counts the clock signal to the second predetermined value.
In order to achieve another aspect of the present invention, a radio communication apparatus includes a receiving section, a power supply section and a control section. The receiving section receives a radio signal, when an electrical power is supplied in a state in which a frame synchronization is established, the radio signal having a preamble field for storing a preamble pattern. The power supply section supplies the electrical power to the receiving section in response to a supply start signal and stops the supply of the electrical power to the receiving section in response to a supply stop signal. The control section generates the supply start signal at a start timing of the preamble field and generates the supply stop signal when presence of the preamble pattern can not be detected from the radio signal received by the receiving section.
In order to achieve still another aspect of the present invention, a radio communication apparatus includes a receiving section, a power supply section and a control section. The receiving section receives a radio signal, when electrical power is supplied in a state in which a frame synchronization is established, the radio signal having a preamble field for storing a preamble pattern. The power supply section supplies the electrical power to the receiving section in response to a supply start signal and stops the supply of the electrical power to the receiving section in response to a supply stop signal. The control section generates the supply start signal earlier than a start timing of the preamble field by a predetermined time and generates the supply stop signal when presence of the preamble pattern can not be detected from the radio signal received by the receiving section.
In order to achieve yet sill another aspect of the present invention, an intermittently receiving method in a synchronization establishing state in a radio communication apparatus, includes:
receiving a radio signal by a receiving section when an electric power is supplied to the receiving section, the radio signal having a preamble field for storing a preamble pattern;
supplying the electrical power to the receiving section;
stopping the supply of the electrical power to the receiving section in response to a supply stop signal; and
generating the supply stop signal when presence of the preamble pattern can not be detected from the radio signal received by the receiving section.